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《化学进展》2017,(Z2)
本文系统总结了非对称氮杂环丁烷的区域选择性开环反应。氮杂环丁烷的开环反应主要包括亲核开环、Stevens重排扩环及消除开环反应等。其中,亲核开环反应是氮杂环丁烷的主要开环方式。开环的区域选择性与氮杂环丁烷取代基结构密切相关。氮杂环丁烷相对比较稳定,其开环通常需要路易斯酸催化或者先转化成季铵盐才可以发生,因此,其开环反应的区域选择性受电子效应的影响比较明显。邻位带有不饱和官能团的氮杂环丁烷及其季铵盐一般发生氮原子与带有不饱和官能团的碳原子之间化学键的断裂,这是因为如芳基、烯基、氰基、酰基、甲酸酯基和甲酰胺基等不饱和官能团的共轭效应可以稳定其连接的碳原子在开环时形成的过渡态或者中间体,使该C—N键更容易断裂。如亲核开环反应,亲核试剂一般进攻芳甲位、烯丙位或连有氰基或甲酸酯基或甲酰胺基的邻位碳原子,电子效应起主要作用。对于2-烷基取代的氮杂环丁烷及其季铵盐,大位阻或者亲核性强的亲核试剂的开环反应一般发生在位阻小的氮邻位碳原子,空间效应起主要作用。分子内的亲核开环反应主要受反应过程中环大小的控制,一般有利于经过三元环、五元环、六元环和七元环过程开环得到开环产物。氮杂环丁烷是一类非常重要的含氮杂环化合物,通过总结和分析氮杂环丁烷的开环反应及其区域选择性,可以更好地认识和利用这类反应,通过有效地预测和控制开环反应的方向,来制备所需的有机化合物。希望本文能够促进氮杂环丁烷开环反应在有机化学中的发展与应用。 相似文献
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在氢氧化钾存在下,1,4,7,10-四氮杂环十二烷与溴乙酸进行N-羧甲基化反应,得到N,N′N″N-四乙酸1,4,7,10-四氛杂环十二烷(DOTA,I),经重结晶纯化,产率88.1%.在碳酸钾存在下,1,4,8,11-四氮杂环十四烷与溴乙酸卡酯进行反应,生成N-乙酸苄酯中间体.该中间体在室温和4.04×105Pa氢气压力下,用Pd/C地催化氢解脱苄基得到N,N′N″N-四乙酸1,4,8,11-四氮杂环十四烷(TETA,Ⅲ),产率56.0%。 相似文献
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含茂基稀土金属有机络合物催化剂在有机合成中的应用 总被引:2,自引:0,他引:2
综述了含茂基稀土金属有机络合物催化下的不饱和烃(或其取取衍生物)转化反应及其在有机合成中的作用。重点阐述了含茂基稀土金属有机络合物催化的烯烃氧化,氢化环化;烯烃和炔烃的氢化硅化,1,5-或1,6-二烯或烯炔的氢化硅化/环化,氨基取代烯烃,炔烃,丙二烯等的氢化胺化/环化等反应在有机合成中的主要用途,这些反应在形成碳-杂原子键,碳-碳键,碳环和杂环等方面具有广泛的应用前景。讨论了这些反应的催化循环机制,区域稳定性,对映选择性,非对映选择性及其影响因素。 相似文献
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关键词:有机电合成·自由基电化学·杂环化合物P.Xiong,H.C.Xu.Chemistry with Electrochemically Generated N-Centered Radicals.Acc.Chem.Res.,2019,52,3339-3350.有机电合成是电化学的重要分支科学,电生自由基反应已成为合成杂环化合物的重要途径.相比于碳自由基化学,氮自由化学研究相对缺乏,主要是缺少便捷、通用的氮自由基形成方法.厦门大学徐海超教授课题组以稳定易得的N-H键为氮自由基前驱体,采用电氧化反应高效可控地生成氮自由基,利用该活性中间体实现了系列传统方法难以进行的高选择性电氧化偶联反应,为多种重要杂环结构提供高效、绿色合成新路线.该综述对电生氮自由基反应研究进行了系统总结,阐释了电氧化形成氮自由基的原理、方法及其在合成化学中的应用. 相似文献
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Maxim E. Dmitriev 《Tetrahedron letters》2010,51(19):2613-269
A new and milder version of the procedure for the synthesis of N-protected α-aminoalkylphosphorylic compounds by reaction of alkyl carbamates, aldehydes and hydrophosphorylic compounds in acetic anhydride/acetyl chloride and a new mechanism for this type of reaction are described. The isolation, for the first time, of N,N′-benzylidene- and N,N′-alkylidenebiscarbamates as intermediates from the reaction medium and studies of the direct reaction of pre-obtained biscarbamates and hydrophosphorylic compounds in acetic anhydride are reported. A new version of the mechanism for this reaction which includes an Arbuzov-type reaction is proposed. 相似文献
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A simple method for the determination of thiuram disulphides was developed. These compounds induce the iodine-azide reaction after cleavage of the SS bond. The consumption of iodine in this reaction is proportional to the amount of the inductor. Inducing properties of the compounds examined were estimated from an induction coefficient ([I]/[S]) which indicates how many times the consumption of iodine in the induced reaction is higher than that in the iodimetric reaction. Under analytically optimum conditions the induction coefficients are in the range 176–211 for eight thiuram disulphides. The identical behaviour of thiuram disulphides in the induced reaction and of the corresponding dithiocarbamates allows the analysis of their mixture in the same sample. The method is sensitive, selective, accurate, cheap and rapid. Other compounds that induce the iodine-azide reaction interfere. 相似文献
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M. K. Beklemishev I. V. Nikolaev L. Yu. Belyaeva 《Moscow University Chemistry Bulletin》2007,62(6):335-342
Polymerization of methyl methacrylate (MMA) and 4-vinylpyridine (VP) has been carried out in an aqueous solution in the presence of the initiating system persulfate-tetramethylethylenediamine. The reaction rate has been monitored by measuring the light absorbance of the suspension of the resulting polymer. The effect of 26 model organic compounds on the polymerization rate has been studied. It has been shown that the VP polymerization is inhibited by a smaller number compounds (9 compounds) than the MMA polymerization (22 compounds), which indicates that the former reaction has better selectivity, whereas the determination of model compounds using the MMA polymerization reaction is more sensitive. This is explained by the lower chain growth rate constant for VP vs. MMA and different stationary concentrations of radicals in the systems. The use of these indicator polymerization reactions makes it possible to distinguish some closely related compounds, e.g., 1,4-benzoquinone and 9,10-anthraquinone (MMA reaction) or dinitrophenol and 4-nitrophenol or phenol (VP reaction). Determination of ascorbic acid in a pharmaceutical formulation has been carried out. 相似文献
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The bromination reaction of azo compounds with N-bromosuccinimide in acetic acid medium has been studied. Some reaction products have been isolated and reaction mechanisms suggested. The reaction study has been applied for the determination of 2-10 mg of azo compounds. The maximum deviation of the results from the theoretical value is generally within +/- 1%. 相似文献
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Merino E 《Chemical Society reviews》2011,40(7):3835-3853
Azobenzenes are ubiquitous motifs very important in many areas of science. Azo compounds display crucial properties for important applications, mainly for the chemical industry. Because of their discovery, the main application of aromatic azo compounds has been their use as dyes. These compounds are excellent candidates to function as molecular switches because of their efficient cis-trans isomerization in the presence of appropriate radiation. The classical methods for the synthesis of azo compounds are the azo coupling reaction (coupling of diazonium salts with activated aromatic compounds), the Mills reaction (reaction between aromatic nitroso derivatives and anilines) and the Wallach reaction (transformation of azoxybenzenes into 4-hydroxy substituted azoderivatives in acid media). More recently, other preparative methods have been reported. This critical review covers the various synthetic methods reported on azo compounds with special emphasis on the more recent ones and their mechanistic aspects (170 references). 相似文献
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Nenajdenko V. G. Korotchenko V. N. Shastin A. V. Balenkova E. S. 《Russian Chemical Bulletin》2004,53(5):1034-1064
The review is devoted to a new catalytic olefination reaction (COR) discovered by the authors. This is the reaction between N-unsubstituted hydrazones of carbonyl compounds with dihalides CHal2XY in the presence of copper(i) chloride to give substituted alkenes. Catalytic olefination is versatile. Variation of the carbonyl and olefinating components opens up the way for the synthesis of various classes of unsaturated compounds including those containing functional groups. The reaction mechanism is discussed and a catalytic cycle describing the process is proposed. A model for estimating and predicting the reactivity of halogen-containing compounds in the COR is developed. The relationship between the structure of the carbonyl substrates and their behavior in the title reaction is elucidated. 相似文献
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A. S. Berenblyum Hussein Ali Al-Wadhaf E. A. Katsman V. R. Flid 《Kinetics and Catalysis》2011,52(2):296-304
The kinetics of the reduction of Pd(II) compounds by dihydrogen on the surface of a carbon support has been investigated for
palladium acetate as an example. A kinetic model has been constructed for this reaction. An autocatalytic mechanism is suggested,
in which the key role is played by Pd(0) compounds and their hydrides. The reaction occurring on the support surface is compared
with the same reaction in solutions of palladium phosphine acetate complexes, where a similar mechanism is observed. One of
the most important features of the surface reaction is the relatively slow reduction of the Pd(I) compounds to Pd(0). This
makes it possible to obtain materials with a high Pd(I) content of 5% and above. 相似文献
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Wei-Li Dong Wen-Xi Cai Rui Wu Zheng-Ming Li 《Phosphorus, sulfur, and silicon and the related elements》2016,191(7):980-983
Benzenethiol, as a reductive agent for the dehalogenation of various α-halocarbonyl compounds, is investigated in the K+/CH3CN system. The reaction affords the reduced compounds in high yields under mild reaction conditions, especially α-chlorocarbonyl compounds. Furthermore, the reaction performed under ultrasonic irradiation greatly shortens the reaction time. 相似文献
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Trifluoroacetic anhydride-mediated solid-phase version of the Robinson-Gabriel synthesis of oxazoles
A traceless solid-phase synthesis of oxazoles 4 via Robinson-Gabriel reaction of solid-supported alpha-acylamino ketones 2 has been achieved. The reaction requires that the cyclization precursor be linked to a benzhydrylic-type linker (compounds 2) and that trifluoroacetic anhydride be used as the cyclodehydrating agent. The solvent has a dramatic effect on the latter reaction, which goes to completion and follows a cyclative-type mechanism only when an ethereal solvent is used. Different synthetic routes have been investigated toward assembling compounds 2. The most straightforward one, which we have validated more extensively, comprises the reaction of Merrifield alpha-methoxyphenyl (MAMP) resin with an alpha-amino ketone to form compounds 1, which are, in turn, acylated. Other methodologies and strategies allowing for the synthesis of compounds 1 that have been investigated include direct alkylation of Rink amide resin; reductive amination of the latter with alpha-keto aldehydes; reaction of MAMP resin with alpha-amino alcohols, followed by oxidation; and protection of Rink amide resin with either 2,4-dinitrosulfonyl or allyl group, followed by alkylation and removal of protecting group. In addition, we disclose a novel variant of the Ugi four-component reaction that allows for the preparation of compounds 2 in a single synthetic step. 相似文献